The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 2 |
| 5 | 3 |
| 6 | 3 |
| 7 | 3 |
| 8 | 4 |
| 9 | 5 |
| 10 | 6 |
| 11 | 12 |
| 12 | 16 |
| 13 | 20 |
| 14 | 31 |
| 15 | 50 |
| 16 | 70 |
| 17 | 106 |
| 18 | 143 |
[0,0,1,2,2,3,3,3,4,5,6,12,16,20,31,50,70,106,143] |